Devicees for controlling the rate of flow of a fluid, primarily but not necessarily a liquid, to provide a substantially constant flow rate over a range of varying line pressures, are utilized in a wide variety of applications. Typical examples, which are by no means all inclusive, are beverage dispensers, automatic washing machines for clothes or dishes, water softeners, hydraulic and pneumatic systems, automotive fuel injection, gas valves, pneumatic machine tools and respiratory controls.
One type of flow control which has been found effective over this wide variety of installations is a centrally apertured rubber washer, which can be routinely engineered to maintain a constant flow rate over a limited range of variations in line pressure. Regardless of the specific application, generally such a flow control washer is designed by specifying an elastomeric material having a requisite modulus of elasticity, thickness, diameter, contour and flow aperture diameter to give the desired rate of flow over the range of supply pressures likely to be encountered in the specific application for which the flow control is needed.
Thus in a typical application according to conventional practice, the flow control is an essentially flat rubber washer having a centrally located flow passage of circular section, which may be countersunk at its downstream end or both ends. In operation, this washer will remain in substantially unstressed condition at the lower end of the supply pressures for which it is designed. If, however, the pressure rises, the washer will bow or deflect in the flow direction, and the resuling distortion will reduce the effective flow area of the flow passage therethrough.
As noted, each flow control of this type is effective over a limited range of inlet pressures, which is taken into consideration, according to the skill of the art, in designing each such control. However, co-owned Jurjevic et al. U.S. Pat. No. 4,609,014 discloses a flow control assembly which includes a control washer and means for changing the nominal flow rate for a range of flow pressures.
Conventionally, washers of this type are used with a seat of rigid material, metal or plastic, which coacts with the washer to provide the desired flow rate, usually by interaction of the flow washer with a specific seat shape. Thus it is a common procedure to design both the properties of the flow control washer and the contour of the seat with which it is to interact to obtain the flow charactertistics required for a specific installation.
While flow controls constructed of thermoset rubber are extremely versatile with respect to the broad range of applications, as noted above, in which they are utilized, it should be noted that scrap or reject rubber material cannot be simply reprocessed, but is usually simply discarded, thereby necessarily affecting the price of the usable rubber flow controls.